Muwatta Malik, Book 29, Hadith 105 (USC-MSA)

Yahya related to me from Malik that he had heard that Umm Salama, the wife of the Prophet, may Allah bless him and grant him peace, said to a woman in mourning for her husband whose eyes were troubling her and the pain had become very strong, "Apply jala kohl at night and wipe it off in the day."

وَحَدَّثَنِي عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ أُمَّ سَلَمَةَ، زَوْجَ النَّبِيِّ صلى الله عليه وسلم قَالَتْ لاِمْرَأَةٍ حَادٍّ عَلَى زَوْجِهَا اشْتَكَتْ عَيْنَيْهَا فَبَلَغَ ذَلِكَ مِنْهَا اكْتَحِلِي بِكُحْلِ الْجِلاَءِ بِاللَّيْلِ وَامْسَحِيهِ بِالنَّهَارِ ‏.‏

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also referenced under: Book 29, Hadith 1270 (In-Book)